Insulated shaft coupling device



1366- 1963 s. F. LETO INSULATED SHAFT COUPLING DEVICE Original Filed Dec. 6, 1960 FIG. 3

INVENTOR.

SALVATORE F. LETO ATTORNEYS United States Patent 3,112,625 HfldULATEl) SHAFT QUUPLEN'Q DEVZQE olvatore F. Leto, 75 College Ave, Arlington, Mass. Continuation of application Ser. No. 74,154 Dec. 6, 196%. This application 31113! 24 1%2, Ser. No. 213,56 2 ill-aims. (Cl. 648) This invention relates in general to drive couplings for transmitting rotational motion from one shaft to another, and more particularly concerns an electrically insulated flexible coupling whic is free to move in axial translation and also able to accommodate slight axial misalignmerit between the shafts.

In certain applications, such as servo-drive systems, it is desirable to couple a pair of shafts which may be slightly misaligned axially or which rotate eccentrically. in many instances it is also desirable that the two shafts having driving connection and yet be electrically insulated one from another.

It is an object of the present invention to provide a novel coupling device of simple construction which may be used to transmit rotary motion from one shaft to another.

Another object of this invention is to provide a flexible coupling device for connecting a pair of rotatable shafts that are axially misaligned and at the same time electrically insulated from one another.

Yet another object of this invention is to provide a flexible, telescopic coupling device having inherently low back-lash characteristics.

More particularly, this invention features a coupling device having a pair of tubular hubs drivingly connecte to one another by a plug. Opposite ends of the plug are pivotally mounted within each of the hubs and are arranged for limited sliding engagement t rerewith.

As another feature of this invention, the plug connecting the two hubs is fabricated from an electrical insulating material, such as nylon, and mounted in such a ner as to limit the longitudinal scope and thereby prevent the hubs from coming into direct contact with one another.

These and other features of the invention, along with further objects and advantages thereof, will become more readily apparent upon a detailed description of a preferred embodiment thereof with reference being made to the accomranyiug drawings, in which:

G. l is a longitudinal cross section of a coupling device made according to this invention;

FIG. 2 is a cross-sectional iew taken along the line 22 of FIG. 1; and

HQ. 3 is a cross-sectional view taken along the line 33 of FIG. 1.

Referring now to the drawings, there is illustrated a coupling device in which a pair of tubular outer hubs lb and 12 are held captive on opposite ends of a cylindrical plug Each outer hub is in the form of a socket bored at one end to receive a shaft, as shown at 16 and 13, and recessed at its other end to form a center cylindrical chamher as at 26 and 2 2, terminating at its inner end in an annular shoulder as at 24 and 26. Both hubs may be made from stainless st el or the like and are radially tapped to receive set screws 28 and 3% for locking the hubs on their respective shafts. It will be observed in PEG. 1 that each hub is provided with an opposed pair of shallow grooves or raceways 32 and 3 which extend lengthwise along the walls of the cylindrical chamber and terminate at one end at the annular shoulders 24 and 21: and at tie opposite end at an inwardly turned lip or stop 36. Preferably the pair of grooves for the hub are oriented 93 about the coupling axis relative to the pair of grooves for the hub 12.

Patented Bee. 3, 1953 ice The plug 14 preferably is molded or machined from an electrical insulating high impact plastic material such as nylon, Teflon or the like and is formed with a reduced center portion and enlarged end portions. A pair of metal bearing balls 33 and 40 are seated 180 apart in the recesses near each end of the plug 14 with each pair being oriented at a angle relative to one another.

The bearing balls are non-rotatably embedded in recesses provided for them in the enlarged end portions of the plug 14 and extend radially out from the surface of the plug to seat firmly in the grooves 32 and 34- with a minimum amount of play between the balls and grooves. The balls 38 and 40 are axially slidable along their grooves so that the coupling device may telescope to a certain extent and accommodate variations in the distance between the shafts which are to be connected. The lip 36, by engaging the balls 43, limits the outward extension of the coupling while the annular shoulders will butt against the ends of the plug 14 when the device is fully contracted and the central chamber nearly closed.

it is desirable that the hubs It and which normally are formed from electrically conductive material, should not be allowed to contact one another at any time. To t is end, the plug 14 has been made long enough so that the opposing inner ends of the two hubs will remain spaced from one another by more than the length of the plug even when the device is fully contracted.

From the description thus far, it will be obvious that the coupling device not only may telescope, but also may deflect within certain limits to accommodate misalignment between the shafts l6 and 18 or an eccentricity in the rotation of those shafts.

Limited flexibility is provided by means of the pivoted connection provided by the balls 33 and ed between the hubs and the plug. The plug has an outside diameter somewhat smaller than the inside diameter of the cylindrical chambers Eli and 22 to define annular spaces between the plug and the inner walls of the chambers. Since the hub 18 is free to pivot about an axis normal to the plane of the paper in 516. l and the hub 12 is free to pivot about the axis parallel with the plane of the paper, the coupling accommodate any misalignment between the shafts 16 and 18 within the limits of the annular spaces between the plug and the inner walls of tie hubs.

It will be understood that in the coupling device illusrated the plug and the hubs can pivot with respect to one another only within a relatively small angle because of the restrictions in space between the plug and the inner walls of the hubs. This angular movement could be increased to some extent by reducing the outside diameter of the plug so as to create additional space within which the parts may move.

The tolerances of the several members should be close enough to permit sliding movement of the balls in their grooves without play or binding. The nylon plug possesses a certain amount of resiliency and takes up whatever backlash that might exist.

it will be appreciated that the coupling device described herein has a simple yet rugged construction. The device may be produced quite inexp nsively and lends itself to miniaturization. Although the invention has been described with particular reference to the illustrated embodiment, it will be obvious that certain modifications may be made. For instance, the bearing balls could be molded into nylon plug as hemispherical bosses if desired and different means may be taken to connect the hubs to their respective shafts.

The present application is a continuation of my copending application Serial No. 74,154, filed December 6, 1960, now abandoned, and entitled insulated Shaft Coupling Device."

Having thus disclosed my invention, what I claim and desire to secure by Letters Patent is:

1. A flexible, electrically non-conductive coupling, comprising a pair of tubular metal hubs bored for connection with shafts to be coupled, opening toward each other and together forming an elongated central chamber of substantially uniform dimensions from end to end, each of the said hubs having a pair of longitudinal grooves in the inner Wall of the central chamber, said grooves being oriented 90 from each other about the longitudinal axis of the chamber and each terminated at its outer end by a radially extending lip, and a cylindrical plug of electrically non-conductive, resilient, plastic mate ial located within the central chamber and being of greater length than the chamber and so preventing contact of the adjacent ends of the metal hubs, the plug having a central portion of reduced diameter and enlarged cylindrical ends containing balls arranged to slide in the longitudinal grooves of the hubs, said plug being restrained and located with respect to said hubs only by said balls.

2. A flexible coupling, comprising a pair of tubular metal hubs bored for connection with shafts to be coupled, opening toward each other and together forming an elongated central chamber of substantially uniform dimensions from end to end, each of the said hubs having a pair of longitudinal grooves in the inner Wall of the central chamber, grooves being oriented at an angle from each other about the longitudinal axis of the chamber and each terminated at its outer end by a radially extending lip, and a cylindrical plug located within the central chamber and being of greater length than the chamber and so preventing contact of the adjacent ends of the metal hubs, the plug having a central portion of reduced diameter and enlarged cylindrical ends containing balls arranged to slide in the longitudinal grooves of the hubs, said plug being restrained and located with respect to said hubs only by said balls.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A FLEXIBLE, ELECTRICALLY NON-CONDUCTIVE COUPLING, COMPRISING A PAIR OF TUBULAR METAL HUBS BORED FOR CONNECTION WITH SHAFTS TO BE COUPLED, OPENING TOWARD EACH OTHER AND TOGETHER FORMING AN ELONGATED CENTRAL CHAMBER OF SUBSTANTIALLY UNIFORM DIMENSIONS FROM END TO END, EACH OF THE SAID HUBS HAVING A PAIR OF LONGITUDINAL GROOVES IN THE INNER WALL OF THE CENTRAL CHAMBER, SAID GROOVES BEING ORIENTED 90* FROM EACH OTHER ABOUT THE LONGITUDINAL AXIS OF THE CHAMBER AND EACH TERMINATED AT ITS OUTER END BY A RADIALLY EXTENDING LIP, AND A CYLINDRICAL PLUG OF ELECTRICALLY NON-CONDUCTIVE, RESILIENT, PLASTIC MATERIAL LOCATED WITHIN THE CENTRAL CHAMBER AND BEING OF GREATER LENGTH THAN THE CHAMBER AND SO PREVENTING CONTACT OF THE ADJACENT ENDS OF THE METAL HUBS, THE PLUG HAVING A CENTRAL PORTION OF REDUCED DIAMETER AND ENLARGED CYLINDRICAL ENDS CONTAINING BALLS ARRANGED TO SLIDE IN THE LONGITUDINAL GROOVES OF THE HUBS, SAID PLUG BEING RESTRAINED AND LOCATED WITH RESPECT TO SAID HUBS ONLY BY SAID BALLS. 